Increasingly, vehicles are being equipped with autonomous and/or semi-autonomous driving mechanisms providing automated diving controls where less driver intervention is required. Though only a few vehicles today may have been created to be fully autonomous (i.e. capable of driving from point A to point B without any driver intervention), many commercially-available vehicles today may employ autonomous and semi-autonomous features.
Cruise control systems, for example, have long been available where a driver sets the speed of the vehicle and the vehicle automatically controls the throttle. Adaptive cruise control systems have been developed too, where the system maintains a set speed and also automatically slows the vehicle if the system senses the vehicle is approaching a slower-moving vehicle. Commercially available autonomous parking systems may automatically provide steering controls to park a vehicle. Further, semi-autonomous, or “driver-assist” features, such as steering-torque assist or steering angle assist, automatically intervene if the driver makes a harsh steering maneuver that could affect vehicle stability.
In autonomous and semi-autonomous control systems, an automated lane centering (LC) system may provide automatic steering control for a vehicle, for example to center a vehicle in a lane as the vehicle moves on a curving road. An LC control system may allow a driver to be distracted, or even to not hold the steering wheel, while an LC system is engaged. An LC system may be incorporated into or used in connection with an electrical power steering (EPS) system in a vehicle. In such a configuration, the LC system may use electronic steering controls to turn the vehicle wheels (e.g. using a motor to move the steering column of the vehicle and thereby turning the vehicle wheels). By its use of the EPS system, an LC system may maintain the position of vehicle, for example, in the center of the lane in question. A LC system may also be used in applications such as lane changing.
U.S. patent application Ser. No. 12/143,439 entitled “PATH GENERATION ALGORITHM FOR AUTOMATED LANE CENTERING AND LANE CHANGING CONTROL SYSTEM,” and U.S. patent application Ser. No. 12/399,317 entitled “MODEL BASED PREDICTIVE CONTROL FOR AUTOMATED LANE CENTERING/CHANGING CONTROL SYSTEMS,” both assigned to the assignee of this application and both herein incorporated by reference, disclose systems and methods for providing path generation for lane centering and lane changing in an autonomous or semi-autonomous vehicle.
Where the LC system uses an electrical power steering (EPS) system for its automatic steering control, it is possible that the EPS system could fail (for example, by communication system failure, control processor crash, mechanical problem in the steering system, etc.). In such a situation, an LC system could not, upon the failure, provide automatic steering control, because the system's ability to control the vehicle's steering would be cut-off. In some circumstances, a failure of an EPS system may cause the front wheels of the system to lock in their current steering angle position, causing further risk of vehicle accident.
Thus, a challenge to safety is presented in an LC system in the event of a failure such as an EPS system failure.